The present invention concerns a flow regulator for gaseous substances, in particular for air in air-conditioning and ventilation installations, serving to maintain the volumetric flow of a gaseous substance at desired magnitude with sufficient accuracy when the differential pressure across the flow regulator varies within given limits, said flow regulator comprising an envelope and a regulating member turnably disposed in a flow passage confined by the envelope, and which, when the differential pressure increases, turns progressively towards a position at right angles to the direction of flow, the torgue exerted by the flow of the gaseous substance on the regulating member and on the other hand a countertorque dependent on the position of the regulating member causing the regulating member turning in the flow passage to assume a position of equilibrium in which the required pressure drop is obtained for keeping the volumetric flow at predetermined magnitude.
In low pressure regulators of prior art, which allow fairly wide regulation of the volumetric flow set-point, the lowest pressure at which the means starts to operate increases with increasing volumetric flow rate. Even at small volumetric flows, the lowest pressure is usually relatively high. The high end pressure also increases with increasing volumetric flow rate set-point.
Because the lowest pressure is high and/or because it depends on the volumetric flow set-point value, the regulators of prior art, in order to function, require extra blower energy and possibly a bigger blower; owing to the increase of pressure they tend to cause noise problems; they impede the designing work, and they cause difficulties in the implementation phase of the installation.
In general, the accurate and stepless setting of the volumetric flow in flow regulators at the site of installation with accuracy and steplessly is exceedingly difficult and often impossible in practice, particularly if the regulator has been installed already, and it is also a fact that the flow rate setting cannot be directly read. Regulators of prior art also do not allow the throttling pressure to be read with which the regulator impedes the flow. It is true that in certain regulator designs of the prior art, one may observe from the outside whether the regulator is within its operating range, but they allow no regulation of the volumetric flow rate.
A prerequisite of serial manufacturing, storing, distribution and convenient use of regulators is that they can with ease and accuracy be regulated at the site of installation, also after installation. It is important with a view to the balancing and inspection of an air-conditioning installation that it is possible to observe from outside the regulator which set-point value of volumetric flow has been selected, whether the regulator is within its operating range, and how strongly the regulator throttles the flow.
In addition, the basic construction and the manufacturing technology of the regulator shall be such that the required calibration measures are as simple and as few as possible and independent of the setting of volumeteric flow. In regulators known at present, the movement of the regulating member cannot be steplessly limited. Therefore, regulators of prior art cannot be used at all for mere balancing based on so-called single pass regulation, which would eliminate the risk of binding of the means. Secondly, regulators of prior art cannot be used for restricted and controlled correction. Thirdly, regulators of prior art cannot be used in the best possible way in air-conditioning installations where the air quantities are varied, e.g. different air quantities in the daytime and during the night.
In the regulators of the prior art, the force that is used to counteract the regulating member is a mass or a spring, or a spring and bellows in combination. Each design has its advantages and disadvantages. Disadvantages connected with the use of springs are e.g. their relaxing, inaccuracies of manufacture, liability to suffer damage, etc. Disadvantages encountered when a mass is used as counterforce are the facts that the regulator can only be installed in a horizontal duct or passage, that the axis has to be horizontal with reference to the direction of flow at all times and that the mass must always be on one and the same side of the passage. Advantages of a mass in the role of counterforce are, for instance, reliability in use, manufacturing accuracy and permanence. Disadvantages of the use of springs combined with bellows are that the design is more liable to disturbances and more expensive than a mere spring and has a shorter life span.
In regulators of prior art a particular damping means is required to allay the oscillations, or hunting, of the regulating member. In some designs of prior art, damping of the dashpot type is used. In another regulator of the prior art, bellows type damping is used. Disadvantages of the damping designs described above are, for instance, that the damping designs may in the course of time either bind or be blocked or break, that they require maintenance, and that they may impair the accuracy.